The present invention relates generally to the molding art and, more particularly, to an improved process for forming preforms used in a molding process.
A process for forming a preform for use in a subsequent molding process is disclosed in U.S. Pat. No. 5,935,509, the disclosure of which is incorporated herein by reference. It involves applying or depositing a layer of discontinuous or chopped mineral (glass) fibers to the sides of a mold or overform having a shape or contour that corresponds to the desired shape of a resultant preform which, in turn, has a shape corresponding to that of a resultant composite product (for example, an open top liner for use in lining a truck bed or the like). The mold is formed of a screen or other perforated support, and the application of the fibers is usually completed by way of spraying them, either separate from or along with a dry (powder) or wet (liquid) binder that is also applied to the mold. A continuous vacuum is applied to a chamber in fluid communication with the mold. The resulting vacuum drawn through the perforations ensures that the chopped fibers and binder are pulled and remain held against the mold during this application step. Once this application step is complete, the composition is subjected to a curing process to cure the binder and hence form the molded article or preform.
The curing process usually requires transporting the mold carrying the composition from the Aspray@ station to a curing station. At the curing station, an overhead convection oven is lowered over the mold and activated to cure the binder. Transporting the molded article or preform to the curing station is usually accomplished by moving the mold on a wheeled trolley, and generally requires first removing the source of vacuum pressure. A necessary precursor to removing the vacuum and/or lowering the oven into place is the placement of large, perforated metal plates called Acompaction screens@over the side and top portions of the mold. These screens not only ensure that the previously applied, uncured composition is held in place, even when the vacuum is removed, but also serve to: (1) protect the composition from making direct contact with the inside surfaces of the oven; and (2) provide a moderate degree of compaction.
After curing is complete and the oven retracted, the mold is transported to a Aremoval@ or recovery station. At this station, the compaction screens are manually removed and the molded article or preform recovered, such as by bodily lifting it from the mold. The operation is then repeated as necessary or desired to form additional molded articles or preforms.
Since the manual placement and removal of even a single compaction screen from the mold is a time consuming and labor intensive operation, automating this aspect of the molding process is generally desirable.
In accordance with a first aspect of the invention, an automated assist apparatus is disclosed for use in a system for forming a molded article from a composition comprised of a plurality of chopped mineral fibers and a binder applied to at least one portion of a perforated mold and initially held in place by a vacuum drawn through the perforations before undergoing a curing process. The apparatus comprises at least one holding device for holding the composition applied to the at least one portion of the perforated mold in place both prior to and during the curing process and a motive device for automatically moving the holding device from a first retracted position away from the mold to a second position for holding the composition in place. As a result of the holding force, the vacuum may be released when the holding device is in the second position, and the composition subjected to the curing process. The holding device may then automatically move to the first retracted position for removing the cured molded article from the mold.
In one embodiment, the holding device includes at least one perforated screen that in addition to holding the composition in place, also serves to at least moderately compact the composition on the corresponding portion of the mold. The holding device may comprise only one such screen having a surface area corresponding to the surface area of the portion of the mold. The motive device may include a first rotatable shaft journaled in a plurality of supports, a support assembly having a first end for supporting the holding device and a second end coupled to the rotatable shaft, and a first motor for selectively engaging and rotating the shaft to move the support assembly and hence the holding device between the first and second positions. In one embodiment, the support assembly comprises a fixed frame having a pair of upper legs, each carrying a bracket for supporting the holding device, and a pair of lower legs having apertures that receive the first rotatable shaft. In a second embodiment, the support assembly includes a pivoting frame including a first subframe forming the first end and a second subframe forming the second end. The first and second subframes are coupled together by a second rotatable shaft such that the second subframe is capable of pivoting relative to the first subframe while the entire support assembly is moved between the first and second positions as a result of the rotation of the first rotatable shaft.
Preferably, the first motor of the motive device has a receiver for coupling with a corresponding coupler on the first rotatable shaft. A mounting assembly comprising an actuator, such as a linear actuator, for moving the motor and hence the receiver toward and away from the corresponding coupler on the first rotatable shaft is also provided. A support stand assembly may also be provided for supporting the first motor, wherein the support stand assembly is capable of moving the first motor between a first retracted position and a second position such that the receiver is in axial alignment with the coupler on the shaft. The support stand assembly may either pivot the first motor between the first and second positions, or raise and lower the first motor between the first and second positions.
In one embodiment, the mold includes a plurality of side portions, and the apparatus further comprises a separate holding device for holding the composition applied to each side portion of the perforated mold in place. A motive device is also provided for automatically moving each separate holding device from a first retracted position to a second position for holding the composition in place. One side of the mold may also be a top portion that together with a plurality of lateral portions defines a box shape for creating a liner having plurality of sidewalls and a base. In that case, the holding device for the top portion is a compaction screen carried in a motive device in the form of an overhead oven that is lowered over the mold to cure the composition and form the molded article.
The motive device may also include a first motor for moving the holding device from the first position to the second position at a spray station where the composition is applied and a second motor for moving the holding device from the second position to the first position at a removal or recovery station after curing is complete. Preferably, a plurality of holding devices and a plurality of the first and second motors corresponding to each of a plurality of sides of the mold are provided at both the spray and removal/recovery stations.
In the case where the side of the mold extends in a vertical direction, the holding device may include a compaction screen for covering the vertically extending side of the mold and a shoulder rail for covering a lower side edge of the composition between the compaction screen and the adjacent side of the mold. A second motive device serves to move the shoulder rail between a first retracted position and a second position adjacent to the mold both before and after curing is complete. The second motive device may comprise at least one pneumatic cylinder for moving the shoulder rail and the apparatus further includes a pneumatic supply apparatus. The pneumatic supply apparatus may be mounted on a laterally translating base for moving to and fro into engagement with a valve block having at least one valve in fluid communication with the pneumatic cylinder. As a result of this mounting, the pneumatic supply apparatus may be retracted before curing and actuated after curing is complete.
In accordance with a second aspect of the invention, a system for forming a molded article from a composition comprised of a plurality of chopped mineral fibers and a binder is disclosed. The system comprises a perforated mold having at least one side portion for receiving the composition, a vacuum source for drawing a vacuum through the perforations in the base, at least one holding device for holding the composition applied to the side portion of the perforated mold in place, and at least one first motive device for automatically moving the holding device from a first retracted position away from the mold to a second position for holding the composition in place. The vacuum is released when the holding device is in the second position, the composition is subjected to a curing process, and the holding device is automatically moved to the first retracted position for removing the cured molded article from the mold.
In one embodiment, the system further includes a trolley for supporting the mold and moving it between a first station where the composition is applied and a second station where the composition is cured. The first motive device may comprise a first rotatable shaft journaled in a plurality of supports, a support assembly having a first end for supporting the holding device and a second end coupled to the rotatable shaft, and a first motor for selectively engaging and rotating the shaft to move the support assembly and hence the holding device between the first and second positions. Preferably, the shaft and support assembly are supported on the trolley and the system further includes a stand assembly for supporting the first motor at the first station. In addition to the first and second stations, the trolley may move the mold to a third station for removing the molded article after curing. In that case, the motive device further includes a second motor at the third station for moving the holding device from the second position to the first retracted position. The second motor may be supported by a separate stand assembly.
In accordance with a third aspect of the invention, an automated process for forming a molded article from a composition including a plurality of mineral fibers applied to at least one side of a perforated mold supported on a stable support structure and held in place by a vacuum drawn through the perforations is disclosed. The process comprises the step of automatically positioning a holding device over the composition applied on the at least one side portion of the mold. As a result, the composition is held in place on the mold in the substantial absence of the vacuum without the need for manual intervention by a worker.
In one embodiment, the holding device is a compaction screen, and the automatic positioning step includes actuating a motive device to move the compaction screen from a first position away from the mold to a second position wherein the composition is held between the compaction screen and the mold. The composition may further comprise a binder, in which case the process further includes subjecting the composition on the mold to a curing process to create the molded article. The process may further include the step of retracting the holding device once the curing process is complete to allow for recovery of the molded article.
In accordance with a fourth aspect of the invention, an automated process for forming a molded article is disclosed. The process comprises the steps of applying a vacuum to a perforated mold having at least one side portion; applying a composition including a plurality of chopped mineral fibers and a binder to at least the side portion of the mold; automatically positioning a holding device adjacent to the side portion of the mold to hold the composition in place when the vacuum is removed; and curing the composition to form the molded article. The method may further comprise automatically removing the holding device from adjacent the side portion of the mold after the curing step and removing the molded article after the holding device is automatically removed.